Atril 2, 1908] 



NATURE 



507 



(P- 33). the imports are lumped together with no 

 allowance for the fact that in some cases large pro- 

 portions arc re-exported, and therefore, except from 

 the point ol view of the shipper, the gross totals 

 throw no light on the industry of the country, in fact 

 they can only mislead. The importance of this 

 allowance for re-exports is shown in the textile 

 group. Thus, of the 52,400,000^. worth of imports 

 of cotton, no less than 7,000,000?. worth was re- 

 exported, and of the wool imports of 26,600,000/. no 

 less than 11,200,000/. If Mr. Bartholomew had these 

 calculations in mind, he would hardly have ventured 

 upon the conclusion he draws in a note to this dia- 

 gram in the following words : — 



" It is at once evident that articles of food greatlv 

 preponderate, the value amounting indeed to 40 per 

 cent, of the total. Raw material accounts for more 

 than 28 per cent., of which 165 represent textile fibres." 



But we would not leave Mr. Bartholomew's atlas 

 without a recognition of the enormous labour it must 

 have involved, and of its successes in several direc- 

 tions. The maps are excellent, and the table of the 

 commodities of commerce and the gazetteer of coun- 

 tries and ports of the world have obvious uses. 



MASONRY AND CONCRETE ARCHES. 

 Symmetrical Masonry Arches. By M. A. Howe. 

 Pp. X+170. (New York: John Wiley and Sons; 

 London : Chapman and Hall, Ltd., j()oh.) Price 

 lox. 6d. net. 



THE author's object in this text-book has been to 

 present in a simple and direct form a method 

 which can be employed in the design of masonry 

 arches according to the elastic theorv. He points 

 out that since such arches are built of materials 

 and under conditions which are more or less un- 

 certain in character, the use of rigidly accurate 

 formula; is not necessary. 



The first portion of the book consists of two 

 chapters, in which the various formula which are 

 required in the design of such arches are deduced, and 

 then several examples are worked out in detail to 

 illustrate the application of the formulae. Indepen- 

 dent formulae are obtained for the effects of bending, 

 axial thrust, and temperature ; these formute are then 

 combined, but the author points out that as the effect 

 of axial stress is small, except in very flat arches, it 

 may in general be neglected in obtaining a combined 

 formula. For symmetrical arches fixed at the ends, the 

 following conditions must be satisfied, viz., the central 

 angle and the relative elevations at the supports must 

 each remain unchanged, and the length of span must 

 remain constant; Mr. Howe is therefore able to 

 obtain three equations involving the three unknown 

 quantities — moment, vertical reaction, and horizontal 

 thrust at the supports of the arch. He then proceeds 

 to deal with a number of special cases of loading, 

 and discusses fully the temperature effects; graphical 

 representations are frequently used to show the results 

 obtained by analysis. 



The last part of this portion of the book is devoted 

 first to a discussion of the trustworthiness of the 

 NO. 2005. VOL. 77] 



elastic theory when applied to ribs composed of natural 

 stone voussoirs, and to plain and reinforced concrete 

 ribs (the author comes to the conclusion that the theory 

 may be used with confidence so long as no tensile 

 stresses occur) ; and secondly to a collection of 

 empirical formulae for the thickness of the ring at 

 the crown and at the supports in stone arches, and 

 for the thickness of the abutments. The examples 

 of the applications of the formulae, which are fully 

 worked out, cover the following cases : — (i) An arch 

 for a single-track railway bridge of 60-feet span and 

 a rise of 8 feet, the arch ring to be constructed of 

 granite; (2) an arch with a clear span of 50 feet and 

 a rise of 10 feet, constructed of reinforced concrete 

 (in both cases the maximum stresses produced by 

 dead load, live load, and changes of temperature are 

 computed) ; (3) the author takes again the data 

 employed in the second example, and gives an in- 

 genious and much shorter method for working out 

 the values of the horizontal reactions and bending 

 moments at different sections of the arch. In the 

 fourth chapter, dimensioned illustrations are given 

 of a few typical arches, and, in the form of an 

 appendix, data have been brought together for 500 arch 

 bridges of masonry, plain concrete, and reinforced 

 concrete. The data in this appendix will be of con- 

 siderable service to engineers who may be called upon 

 to design arch bridges of one or other of these 

 materials. T. H. B. 



OUR BOOK SHELF. 

 Das Kaiisalitatsprinzip der Biologic. By Dr. 



Friedrich Strecker. Pp. viii+153. (Leipzig: \V. 



Engelmann, 1907.) Price 3 marks. 

 Von B.aer said that the chief end of biology was to 

 refer the formative forces of organisms to the general 

 forces and vital directions (Lebensrichtungen) of the 

 Kosmos. According to the mechanists this is rapidly 

 being done ; according to the neo-vitalists this is not 

 being- done at all, for t'ne characteristic activities of 

 living creatures cannot be described in the formulas of 

 physicochemical happenings, and there is in the 

 organism an autonomous regulative force or entelechy. 

 Biologists oscillate between these two positions, or 

 dogmatically entrench themselves in either of them, 

 very much as philosophers did in regard to empiricism: 

 and rationalism before Kant's critique showed a better 

 way. Dr. Strecker seeks to be a daysman between 

 the two biological schools, laying his hands upon them 

 both, pointing out that there is truth on both sides, 

 but that there is a third outlook which dominates both. 

 For the practical methods and analytic results of the 

 " Entwicklungsmechaniker," such as Roux, the 

 author has an appreciative respect; his criticism is 

 epistemological rather than biological; he does not 

 think that there is any hope of rationally interpreting 

 organisms in mechanistic formulae. For the neo- 

 vitalists he has also much that is good to say, for 

 they at least do not give a false simplicity to the facts 

 of life; on the other hand, he does not hold with an 

 "entelechv," which seems to be an ingenuous way of 

 bundling all the difficulties into one term, and saying 

 "there's an end of it." The fact is that the 

 mechanists and the vitalists are tarred with the same 

 stick, they are ekgenctic, they seek to interpret re- 

 sults which have come to be, instead of concentrating 

 attention on the process of becoming, which is the 



